1. Field of the Invention
The present invention relates to a room temperature ferromagnetic semiconductor used for a spin electronic device having wide bandgap semiconductor characteristics and magnetic characteristics at a room temperature, its fabrication method, and a ferromagnetic semiconductor based device.
2. Description of the Background Art
A research on a GaN-based nitride semiconductor was started to fabricate a blue light emitting device in the early 1990, and currently, researches are being actively conducted on various electronic devices in addition to light emitting and light receiving devices.
In forming a triple element compound, an energy gap can be controlled from 1.9 eV to 6.2 eV, so that the nitride semiconductor is used for fabrication of a light emitting device of a wave length region of the entire visible light including an ultraviolet ray region. A blue and green light emitting diode (LED) and a ultraviolet ray detector was successfully commercialized years ago, and a blue light emitting diode (LED0 is anticipated to be commercialized soon.
Meanwhile, research on an electronic device using the nitride semiconductor is actively ongoing. Since a report on a research on a GaN MESFET (metal-semiconductor field effect transistor), a crystal growing technique has been much developed and an electronic device fabrication technique has been also remarkably improved. Diverse researches are being conducted on the electronic device on the basis of excellent physical properties such as a large energy gap, a high thermal and chemical stability, a high electron mobility, a high breakdown voltage and saturation electron speed, the large discontinuation of conduction band, or the like.
Meanwhile, in view of a novel conceptual spintronics (a compound word of spin and electronics, a fresh paradigm intending to develop an electron and an optical device in consideration of freedom of a spin together with the electronic charge of the electron, a research has been ongoing on the applicability of spintronics in the wake of report on ferromagnetic semiconductor characteristics at a temperature of about 110 K by substituting a portion of Ga in GaAs with Mn, a transition metal, by using a molecular beam epitaxy (MBE) process in the late 1990.
In this respect, however, (In,Mn)As (Tc=35K), (Ga,Mn)As (Tc=110K) and MnGe (Tc=116 K) are representative ferromagnetic semiconductors which have been studied up to date, but owing to the low Curie temperature, there is a limitation in fabricating a spin device that can be operated at a room temperature. Therefore, finding a ferromagnetic semiconductor with a Curie temperature above a room temperature is the most critical factor in this field.
According to a theoretical computation result using a Zener model, GaN, ZnO are anticipated to exhibit a Curie temperature above the room temperature, on which, thus, researches are being focussed to testify experimentally.